Use logging print the output of pprint

Question

I want to use pprint's output to show a complex data structure, but I would like to output it using the logging module rather than stdout.

ds = [{'hello': 'there'}]
logging.debug( pprint.pprint(ds) ) # outputs as STDOUT

Answer 1

Use pprint.pformat to get a string, and then send it to your logging framework.

from pprint import pformat
ds = [{'hello': 'there'}]
logging.debug(pformat(ds))

Answer 2

The solution above didn't quite cut it for me because I'm also using a formatter to add name and levelname when logging. It looks a little untidy:

__main__    : DEBUG   : ['aaaaaaaaaaaaaaaaaaaa',
'bbbbbbbbbbbbbbbbbbbb',
'cccccccccccccccccccc',
'dddddddddddddddddddd']
__main__    : DEBUG   : Some other logging text

There may be a more elegant solution, but this:

for line in pprint.pformat(ds).split('\n'):
    logging.debug(line)

produces something a little nicer:

__main__    : DEBUG   : ['aaaaaaaaaaaaaaaaaaaa',
__main__    : DEBUG   :  'bbbbbbbbbbbbbbbbbbbb',
__main__    : DEBUG   :  'cccccccccccccccccccc',
__main__    : DEBUG   :  'dddddddddddddddddddd']
__main__    : DEBUG   : Some other logging text

Answer 3

An alternative is to use json.dumps with the indent arg. In some cases (depending on logging format, data size, etc) it might give you nicer output.

logging.error('Malformed input data!')
logging.error(pformat(foo))

ERROR:root:Malformed input data!
ERROR:root:{'a': 1, 'b': 2, 'c': 'womp rat', 'd': 'turd sandwich'}

vs.

logging.error('Malformed input data!') 
logging.error(json.dumps(foo, indent=4))

ERROR:root:Malformed input data!
ERROR:root:{
    "a": 1,
    "b": 2,
    "c": "womp rat",
    "d": "turd sandwich"
}